Before firmware upgrade:
1. Make sure of the battery level at least over 50%.
2. Make sure of the memory size at least over 500MB.
3. User setting is initialized after upgrade.
4. Before upgrading, please make a backup of important files just in case.
[How to upgrade]
1. Connect to Wi-Fi
2. Find 'new' firmware on Setting - Update - System update
- System stability improvements.